A novel bornane synthesis by an old idea.

Area of Science:

• Organic Chemistry
• Synthetic Chemistry
• Cycloaddition Reactions

Background:

• Spiro[2.4]hepta-4,6-dienes are valuable synthetic intermediates.
• Investigating functionalization at the C-4 position is crucial for expanding their utility.

Purpose of the Study:

• To synthesize spiro[2.4]hepta-4,6-dienes with a carbon substituent at C-4.
• To explore the reactivity of a thiatricycle intermediate derived from spiro[2.4]hepta-4,6-diene.

Main Methods:

• [4 + 2] cycloaddition of spiro[2.4]hepta-4,6-diene with thiophosgene.
• Solvolysis reactions of the resulting thiatricycle with alcohols.
• Desulfurization of thionoesters to form carboxylates.
• Lithium aluminum hydride reduction to yield alcohols.
• Diels-Alder reactions with substituted alkenes.

Main Results:

• Formation of ester mixtures (7 and 8) from solvolysis.
• Synthesis of methyl and ethyl spiro[2.4]hepta-4,6-diene-4-carboxylates (10a,b).
• Preparation of the corresponding alcohol (11).
• Generation of [4 + 2] cycloadducts (12a-c) with ethenetetracarbonitrile.
• Synthesis of a spiro(bicyclo[2.2.1]hept-5-ene-7,1'-cyclopropane) derivative (14a).
• Transformation of 14a to rac-10-hydroxycamphor (17).

Conclusions:

• The developed synthetic route provides access to functionalized spiro[2.4]hepta-4,6-dienes.
• The synthesis of a bornane derivative (rac-10-hydroxycamphor) demonstrates the potential of these intermediates.
• This methodology offers opportunities for further structural variations and applications in organic synthesis.